HA16107P Datasheet, PDF (17/40 Pages) Hitachi Semiconductor – PWM Switching Regulator for High-performance Voltage Mode Control

HA16107P/FP, HA16108P/FP
Application Note
• Case:
When DC power is applied directly as the power supply of the HA16107/HA16108, without using the transformer
backup coil.
• Phenomenon:
The IC may not be activated in the case of a circuit in which V_IN rises quickly (10 V/100 µs or faster), such as that
shown in figure 2.
• Reason:
Because of the IC circuit configuration, the timer latch block operates first.
• Remedy (counter measure):
Take remedial action such as configuring a time constant circuit as shown in figure 3, to keep the V_IN rise speed
below 10 V/100 µs.
If the IC power supply consists of an activation resistance and backup coil, as in an AC/DC converter, The V_IN rise
speed is usually around 1 V/100 µs, and there is no risk of this phenomenon occurring.
Input
V_IN
Output
HA16107
Series
V_IN
GND
Feedback
Figure 2 Example of Circuit with Fast V_IN Rise Time
Input
Time constant _{R 51Ω}
circuit
V_IN
Output
V_IN
18 V
1 µF _C
HA16107
Series
GND
Feedback
Figure 3 Sample Remedial Circuit
Rev.4.00 Jun 15, 2005 page 17 of 39